The present invention relates to composite particles, and a tread rubber composition, a paint and a resin composition using the composite particles, and more particularly, to composite particles capable of an excellent dispersibility and an excellent light resistance; a tread rubber composition prepared by blending the composite particles in rubber, which can show a less discoloration upon exposure to light, a low electric resistance, an excellent wear resistance and an excellent tensile strength; and a paint containing the composite particles and a resin composition containing the composite particles.
The composite particles of the present invention can be used as pigments, or colorants, fillers or the like for rubbers, paints and resin compositions.
As white inorganic particles having a refractive index of less than 2.0, there are generally known extender pigments. The extender pigments form a transparent or translucent dispersion when dispersed in vehicles such as oils and varnishes. Therefore, the extender pigments have been conventionally used as non-color pigments, i.e., as extenders for paints, printing inks or the like. With the progress of powder science or technology, the extender pigments have been recently used not only as extenders, but also as function-imparting pigments in extensive industrial fields for the purpose of controlling or improving the processability and physical properties of rubbers, plastics, paints, printing inks, adhesives, sealing materials, papers or the like.
However, although the extender pigments show transparency or translucency in vehicle, paints or resin compositions to which the extender pigments are added as fillers, exhibit a more whitish color than those containing no extender pigments, and fail to show a sufficient blackness required in some application fields.
White inorganic particles having a refractive index of not less than 2.0 such as titanium oxide, zinc oxide and zirconium oxide, have been conventionally used as white pigments for rubbers, plastics, paints or printing inks.
In particular, it is known that titanium oxide and zinc oxide exhibit an ultraviolet light-shielding effect because these pigments can absorb light in ultraviolet region. In recent years, the titanium oxide and zinc oxide are also used as an ultraviolet light absorber for cosmetics or the like.
However, it is also known that the titanium oxide and zinc oxide have a high surface activity. Therefore, when paints or resin compositions using these pigments are exposed to outdoor environments, there arise problems such as chalking of a painted surface and deterioration of resins.
In addition, white inorganic particles are generally non-conductive, for example, silica particles and zinc oxide have volume resistivity values of about 106 to 108 xcexa9xc2x7cm and about 107 xcexa9xc2x7cm, respectively. Therefore, it is known that in the applications requiring a higher or lower volume resistivity value, it is necessary to use an electric resistance-regulating agent such as carbon black or the like in addition to the white inorganic particles.
On the other hand, black pigments such as aniline black, carbon black or the like have been extensively used in various applications such as inks, paints, rubbers and plastics for the purpose of imparting thereto a tinting property, electric properties, a light-absorbing property or the like.
However, it is known that these black pigments, especially carbon black, are fine particles having an average particle diameter as small as about 0.005 to 0.05 xcexcm and, therefore, it is difficult to disperse carbon black in vehicles or resin compositions. In addition, it is also known that these black pigments are bulky particles having a bulk density as high as about 0.1 g/cm3 and, therefore, are deteriorated in handling property and workability.
Further, since the paints or resin compositions using such black particles are sometimes used in outdoor applications and exposed to direct sunlight or severe weather conditions such as winds and rains, the black particles are required to maintain a good hue and properties thereof for a long period of time, namely to show excellent light resistance and weather resistance.
Consequently, it has been strongly required to provide black particles capable not only imparting thereto various properties such as electric properties, ultraviolet light-absorbing property or the like according to applications thereof, but also exhibiting excellent light resistance, tinting strength and dispersibility in vehicle.
Hitherto, it is known that silica particles are blended together with carbon black in rubbers for the purposes of reduction in electric resistance of the rubbers as well as reinforcement thereof (Japanese Patent Application Laid-Open (KOKAI) No. 52-93452(1977), and Japanese Patent Nos. 2722077, 2788212 and 3160552).
In addition, it is also known that titanium oxide or zinc oxide is coated with a silica-based substance in order to suppress the surface activity (Japanese Patent Application Laid-Open (KOKAI) Nos. 2000-319128 and 2001-58821).
At present, it has been strongly required to provide composite particles capable of not only imparting thereto various properties such as electric properties, ultraviolet light-shielding property, according to the applications thereof, but also exhibiting excellent light resistance, tinting strength, handling property and dispersibility in vehicle. However, conventional composite particles have failed to satisfy all of these requirements.
Namely, in Japanese Patent Application Laid-Open (KOKAI) No. 52-93452(1977) and Japanese Patent Nos. 2722077 and 3160552, there are described carbon-coated silica particles and a rubber composition containing such coated silica particles which are used for tires. However, in any of these, since a carbon black coat is formed on the surface of the silica particle by thermal decomposition of organic compounds, the adhesion of carbon black onto the surface of the silica particle is very weak. Therefore, when the coated silica particles are kneaded in the rubber composition, the carbon black coated is desorbed or fallen-off from the surface of the silica particle, so that a part of the surface of the silica particles is exposed. This results in non-uniform dispersion of the silica particles in the rubber composition, and failure to exhibit sufficient the above-mentioned effects.
The rubber composition described in Japanese Patent No. 2788212 is a tire tread rubber composition containing carbon black surface-treated with 0.1 to 50% by weight of silica. However, the adhesion of silica onto the surface of carbon black is very weak. Therefore, when the coated carbon black is kneaded in the rubber composition, the silica coated thereon is desorbed or fallen-off from the surface of the carbon black, thereby preventing carbon black from being uniformly dispersed in the composition.
Also, in Japanese Patent Application Laid-Open (KOKAI) Nos. 2000-319128 and 2001-58821, there is described zinc oxide or titanium oxide whose surface is coated with silica, silica-based substances such as alkyl-modified silica, zinc silicate or the like. However, the coating formed on zinc oxide or titanium oxide fails to sufficiently reduce the surface activity thereof.
In Japanese Patent Application Laid-Open (KOKAI) Nos. 11-323174(1999) and 2001-11339, there are described iron-based composite particles comprising black iron oxide particles or black iron oxide hydroxide particles as core particles, a coating layer formed on the surface of the core particle which comprises organosilane compounds obtainable from alkoxysilanes or polysiloxanes, and a carbon black coat coated onto the surface of the coating layer composed of organosilane compounds or polysiloxanes. However, these techniques are related to the method of fixedly coating carbon black onto the black iron compound particles. Since the core particles show a magnetism, the obtained composite particles cannot be used in applications in which such a magnetism is unnecessary and unsuitable, and tend to suffer from magnetic agglomeration, resulting in poor dispersibility.
Separately, automobile tires have been required to exhibit a good road grip property even upon running on a wet road in order to attain a high running safety, as well as high wear resistance and high break strength. In recent years, from the standpoints of saving energy and resources, automobile tires having a low-rolling resistance for reducing fuel consumption, i.e., so-called low-fuel consumption tires have been positively developed.
The automobile tires having a high electric resistance tend to generate noises in radio and electronic devices by undesired static discharge due to dielectric breakdown, or tend to cause fire by spark between tire and automobile body due to static electrification thereof, upon fueling. Therefore, the automobile tires have been strongly required to exhibit a low electric resistance.
Conventionally, carbon black is blended in a rubber composition for tires or the like for the purposes of reinforcement, increase of wear resistance or reduction of electric resistance. However, it is known that such carbon black-containing tires have a large rolling resistance, resulting in large fuel consumption of automobiles.
Consequently, tires in which silica particles capable of reducing a rolling resistance as compared to carbon black are blended as a rubber-reinforcing filler, have been proposed and already put into practice (Japanese Patent Application Laid-Open (KOKAI) No. 3-239737(1991)).
However, since the silica particles have a silanol functional group on the surface thereof and, therefore, tend to be agglomerated together by hydrogen bonds between the silanol groups, it has been difficult to uniformly disperse the silica particles in the rubber composition for tires or the like. In addition, it is known that the silica particles show a low compatibility with rubbers ordinarily used for tires because of a hydrophilic property of the silanol group present on the surface thereof, resulting in poorer reinforcing effect as compared to carbon black.
In order to improve the dispersibility of the silica particles in rubbers, there has been proposed the method of treating the surface of the silica particles with an organosilicon compound (Japanese Patent Application Laid-Open (KOKAI) No. 8-245838(1996)).
Further, when the silica particles are used as a reinforcing filler, an electric resistance of tires increase owing to non-conductivity thereof. Therefore, tires using conductive particles such as carbon black in combination with the silica particles have been proposed and already put into practice (Japanese Patent Application Laid-Open (KOKAI) Nos. 52-93452(1977), 3-239737(1991) and 8-245838(1996), Japanese Patent Nos. 2722077, 2788212 and 3160552, etc.).
Furthermore, ordinary automobile tires are colored black and, therefore, have been strongly required to exhibit a high blackness as well as a less discoloration upon exposure to light from the viewpoint of good appearance.
Also, at present, it has been strongly required to provide a tread rubber composition exhibiting a less discoloration upon exposure to light, a low electric resistance, an excellent wear resistance and an excellent tensile strength. However, conventional tread rubber compositions have failed to satisfy all of these requirements.
Namely, the tire tread composition described in Japanese Patent Application Laid-Open (KOKAI) No. 3-239737(1991), comprises 100 parts by weight of a rubber blend containing a styrene-butadiene copolymer prepared by copolymerizing styrene and butadiene in the presence of an organolithium compound, in an amount of not less than 30 parts by weight; 10 to 150 parts by weight of silica particles; and 0 to 100 parts by weight of carbon black. However, since the silica particles are non-uniformly dispersed in the rubber composition, it is difficult to attain excellent wear resistance and tensile strength. In addition, since the silica particles prevent carbon black from being uniformly dispersed, it is difficult to reduce an electric resistance of the obtained composition.
In Japanese Patent Application Laid-Open (KOKAI) No. 52-93452(1977) and Japanese Patent Nos. 2722077 and 3160552, as seen from the above, the adhesion of carbon black to the surface of the silica particle is very weak (shown below in Comparative Examples). Therefore, the silica particles are non-uniformly dispersed in the rubber composition, resulting in deterioration in wear resistance and tensile strength.
As a result of the present inventors"" earnest studies, it has been found that composite particles having an average particle size of 0.001 to 12.0 xcexcm, which comprise white inorganic particles; a gluing agent-coating layer formed on at least a part of the surface of the white inorganic particle, comprising at least one gluing agent selected from the group consisting of organosilicon compounds, various coupling agents such as silane-based coupling agents, titanate-based coupling agents, aluminate-based coupling agents and zirconate-based coupling agents, oligomer compounds and polymer compounds; and a black pigment coat composed of carbon black and/or aniline black, formed on at least a part of the surface of the coating layer composed of the gluing agent in an amount of 1 to 500 parts by weight based on 100 parts by weight of the white inorganic particles, can exhibit an excellent light resistance and dispersibility. The present invention has been attained on the basis of the finding.
An object of the present invention is to provide composite particles exhibiting an excellent light resistance and an excellent dispersibility.
An object of the present invention is to provide black composite particles for a tread rubber composition, which exhibit not only a high blackness and a less discoloration upon exposure to light, but also a low volume resistivity value and an excellent dispersibility
An object of the present invention is to provide black composite particles for a paint or a resin composition, which is capable of not only imparting thereto various functions according to applications thereof, but also exhibiting excellent light resistance, tinting strength and dispersibility in vehicle.
An object of the present invention is to provide composite particles for a paint or a resin composition, which is capable of not only imparting thereto various functions according to applications thereof, but also exhibiting especially an excellent ultraviolet light-shielding property as well as excellent light resistance, handling property and dispersibility in vehicle.
An object of the present invention is to provide a tread rubber composition capable of exhibiting a less discoloration upon exposure to light, a low electric resistance, and excellent wear resistance and tensile strength.
An object of the present invention is to provide a paint or a resin composition capable of exhibiting a high blackness, a more excellent light resistance and a more excellent storage stability.
An object of the present invention is to provide a paint or a resin composition capable of exhibiting a more excellent light resistance and a more excellent storage stability.
To accomplish the aims, in a first aspect of the present invention, there are provided composite particles having an average particle diameter of 0.001 to 12.0 xcexcm, comprising:
white inorganic particles as core particles;
a gluing agent-coating layer formed on at least a parts of the surface of said white inorganic particle; and
a black pigment coat composed of carbon black, aniline black or both carbon black and aniline black, formed onto at least a part of the gluing agent-coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of said white inorganic particles.
In a second aspect of the present invention, there are provided composite particles having an average particle diameter of 0.001 to 12.0 xcexcm, comprising:
white inorganic particles as core particles;
a coating layer formed on at least a parts of the surface of said white inorganic particle, comprising at least one compound selected from the group consisting of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of silicon,
a gluing agent-coating layer formed on at least a parts of the surface of said coating layer; and
a black pigment coat composed of carbon black, aniline black or both carbon black and aniline black, formed onto at least a part of the gluing agent-coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of said white inorganic particles.
In a third aspect of the present invention, there are provided composite particles having an average particle diameter of 0.001 to 0.5 xcexcm, and comprising:
silica particles (1) as core particles;
a coating layer formed on at least a part of the surface of the silica particles (1), comprising organosilane compounds obtainable from alkoxysilanes, or polysiloxanes; and
a carbon black coat formed on at least a part of the surface of the coating layer in an amount of 1 to 500 parts by weight based on 100 parts of the silica particles (1).
In a fourth aspect of the present invention, there are provided composite particles having an average particle diameter of 0.001 to 0.5 xcexcm, and comprising:
silica particles (1) as core particles;
a coating layer formed on at least a part of the surface of the silica particles (1), comprising organosilane compounds obtainable from alkoxysilanes, or polysiloxanes;
a carbon black coat formed on at least a part of the surface of the coating layer in an amount of 1 to 500 parts by weight based on 100 parts of the silica particles (1); and
an outer surface coat formed on at least a part of the surface of the carbon black coat, comprising a fatty acid, a metal salt of fatty acid or a coupling agent.
In a fifth aspect of the present invention, there are provided composite particles having an average particle diameter of 0.001 to 12.0 xcexcm, and comprising:
white inorganic particles having a refractive index of less than 2.0 as core particles;
a gluing agent-coating layer formed on at least a part of the surface of the white inorganic particle; and
a black pigment coat formed onto at least a part of the gluing agent-coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of the white inorganic particles, composed of carbon black, aniline black or both carbon black and aniline black.
In a sixth aspect of the present invention, there are provided composite particles having an average particle diameter of 0.001 to 12.0 xcexcm, and comprising:
white inorganic particles having a refractive index of not less than 2.0 as core particles;
a gluing agent-coating layer formed on at least a part of the surface of the white inorganic particle; and
a black pigment coat formed onto at least a part of the gluing agent-coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of the white inorganic particles, comprising carbon black and/or aniline black.
In a seventh aspect of the present invention, there is provided a pigment comprising composite particles defined in any one of the first to sixth aspects.
In an eighth aspect of the present invention, there is provided a tread rubber composition, comprising:
100 parts by weight of a rubber component; and
10 to 200 parts by weight of the pigment composed of composite particles having an average particle diameter of 0.001 to 0.5 xcexcm, and comprising:
silica particles (1) as core particles;
a coating layer formed on at least a part of the surface of the silica particles (1), comprising organosilane compounds obtainable from alkoxysilanes, or polysiloxanes; and
a carbon black coat formed on at least a part of the surface of the coating layer in an amount of 1 to 500 parts by weight based on 100 parts of the silica particles (1).
In a ninth aspect of the present invention, there is provided a paint comprising:
a paint base material, and
a pigment composed of (i) composite particles having an average particle diameter of 0.001 to 12.0 xcexcm, and comprising:
white inorganic particles having a refractive index of less than 2.0 as core particles;
a gluing agent-coating layer formed on at least a part of the surface of the white inorganic particle; and
a black pigment coat formed onto at least a part of the gluing agent-coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of the white inorganic particles, composed of carbon black, aniline black or both carbon black and aniline black,
(ii) composite particles having an average particle diameter of 0.001 to 12.0 xcexcm, and comprising:
white inorganic particles having a refractive index of not less than 2.0 as core particles;
a gluing agent-coating layer formed on at least a part of the surface of the white inorganic particle; and
a black pigment coat formed onto at least a part of the gluing agent-coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of the white inorganic particles, comprising carbon black and/or aniline black.
In a tenth aspect of the present invention, there is provided a rubber or resin composition comprising:
a base material for rubber or resin composition, and
a pigment composed of (i) composite particles having an average particle diameter of 0.001 to 12.0 xcexcm, and comprising:
white inorganic particles having a refractive index of less than 2.0 as core particles;
a gluing agent-coating layer formed on at least a part of the surface of the white inorganic particle; and
a black pigment coat formed onto at least a part of the gluing agent-coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of the white inorganic particles, composed of carbon black, aniline black or both carbon black and aniline black,
(ii) composite particles having an average particle diameter of 0.001 to 12.0 xcexcm, and comprising:
white inorganic particles having a refractive index of not less than 2.0 as core particles;
a gluing agent-coating layer formed on at least a part of the surface of the white inorganic particle; and
a black pigment coat formed onto at least a part of the gluing agent-coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of the white inorganic particles, comprising carbon black and/or aniline black.